for watching. we'll se this is "world news." tonight, two fast-moving stories. in boston, the breaking news. the fbi says they want everybody to help find these two men on the surveillance tape. persons of interest in the boston marathon bombing. we'll take you frame by frame through the video. why the fbi says, look at every detail. and the breakthrough comes as an emotional president tonight has a message for the bombers. >> we will find you. and, yes, you will face justice. also tonight, that texas disaster. what caused the giant tank at a fertilizer plant to explode and shatter an entire town? the tremors felt miles away as true heroes rushed in to help. in other news, water world.

kayaking down the streets of chicago. floods, cars swallowed in a big hole. the earth no match for the deluge. and the heart of a hero. from boston to texas, the ordinary americans who rushed toward danger. is there a super hero in every one of us? good evening to you, and tonight from texas to boston, we are a nation in pursuit of answers. and as we come on the air tonight, there is stunning news out of boston. the fbi releasing surveillance tapes. two people called persons of interest in the marathon-day bombings. the fbi considers them armed, dangerous, asked that no one approach them. but they ask all members of the public to look at these tapes, to study them in detail and

help. abc's chief investigative correspondent, brian ross, will take us frame by frame through the clues. brian? >> reporter: good evening. federal authorities now believe that a team of at least two men was responsible for the bombings here. as you say, described as armed and extremely dangerous. the fbi is basing its two-bomber theory on these surveillance camera videos and still pictures made public late today. two white men in their 20s, according to the fbi. one with a black cap, the second with a white cap worn backwards. both wearing backpacks that the fbi believe held the bombs. off to the side of this video, runners can be seen heading to the finish line and time code markers indicate the footage was made about 13 minutes before the first bomb went off. the fbi says only one of the two potential suspects, the one with the white cap, was actually seen placing his backpack at the scene of an explosion. >> we are releasing photos of these two suspects.

re identift o. they appear to be associated. >> reporter: officials say they made the images public now becae they nd the faces to names. but they warn these are dangerous men. >> we consider them to be armed and extremely dangerous. >> reporter: there were new developments today based on the some 300 pieces of evidence recovered from the crime scene. some of the components, including this battery, and this circuit board, were recognized by hobbyists as parts of a toy remote control car, similar to this one seen in an online video. the owner of one hobby store outside boston said fbi agents interviewed him last night and left little doubt that a remote controlled unit had been used in the bombs. >> it looked to me that one of the components was a radio receiver. the response i got was dead on. >> reporter: there are instructions on the internet about how to use a remote controlled toy car to set off a bomb, both from "the anarchist

cookbook" and several jihadist sites as well. there is still no indication of whether there was an act of foreign or domestic terrorism, but the president vowed today the bombers, whoever they are, will not escape. >> yes, we will find you. and, yes, you will face justice. >> reporter: what happens next is what one official called an electronic dragnet, pushing these images far and wide to engage the public in the hunt. diane? >> all right, brian. thank you. i want to bring in abc's pierre thomas who has learned new details since the briefing toda. >> a senior law enforcement official tells me e wo suspects is seen in anher vio making a cellphone call around the time of the exns. they believe that the cellphone was used to trigger one of the explosions. the officials said a massive effort is under way to capture every cellphone call in that local area at the time of the bombings, to see if they can trace it back to the bomber. the source said it's a time-consuming process but a top priority.

>> as you watch the tapes go by pierre, and you've studied these so often, tell us the kind of detail the fbi is asking everyone to notice. >> one of the things you can see as you look at the tape is that the black backpack is one critical piece of evidence. my sources are telling me that backpack is the one that they recovered the most material from. the other thing is that every piece of evidence in that frame, the hat, the coat, the pants, they want the public to look at that because there might be something that someone would notice. >> that's right. and to look over every frame by frame, they sent everyone to the website, fbi.gov to check it out. and i know you'll be getting back to the phones as well, pierre. thank you. as we said, the president today delivered a summons, a promise, and a blazing tribute in boston. and abc's linsey davis tells us more. >> reporter: the president came with a simple message. >> if they sought to intimidate

us, to terrorize us, it should be pretty clear by now that they picked the wrong city to do it. [ applause ] >> not here in boston, not here in boston. >> reporter: at times, he brought them to their feet. at others, he brought them to t thsse was always to >> as you begin this long journey ofecer ay, wllityou as t stand and walk and, yes, run again -- of that i have no doubt, you will run again. [ applause ] >> reporter: for those whose cheers were abruptly silenced marathon day, the president today roused them once again. among them families of the victims. and runners, in those signature marathon jackets. >> we may be momentarily knocked off our feet, but we'll pick ourselves up. we'll keep going. we will finish the race.

>> reporter: amid the applause, the anguish, still so fresh from the parishioners to the president himself. the hundreds of people who lined the streets outside of the church here today, they couldn't hear president obama or anyone else inside. they simply stood silently in a show of support. diane? >> and again the president quoting a poem that boston is not a place, it is a state of grace. thanks so much, linsey davis from boston for us tonight. now we turn from boston to the other american region in crisis, reeling tonight and asking the nation's prayers after a massive and mysterious explosion at a fertilizer plant. the image caught on tape. the air thick with the smell of ammonia. volunteer firefighters overwhelmed. the blast had the ferocity of a 2.1 earthquake and the thunderous shock could be heard

45 miles away. tonight, the small towe waco, called west, has been flattened. abc's steve osunsami has been there through the night. >> reporter: their moment of crisis for families in a small town of west, texas, came at 7:29 p.m., with a fire raging at their giant fertilizer depot. >> everybody needs to get away from there. back all trucks away from the plant. >> reporter: a small team of firefighters answering the call, worried the whole thing could blow. then at 7:53, the sound no one here will soon forget. [ blast ] >> are you okay? >> i can't hear. get out of here, please get out of here! >> reporter: the plant blew to pieces. >> we need every ambulance we can get. a bomb just went off inside here. it's pretty bad. >> reporter: a mushroom cloud of smoke filled the sky. >> what is it? >> i don't know. >> it looked like, you remember seeing atomic bomb, you know, that plume. well, there it was. >> reporter: by 8:15 there were five firefighters missing, two

>> we got a lot of firemen down. >> reporter: the nursing home across the street, blasted. a nearby apartment building destroyed. >> oh, my god. >> reporter: at 8:30, betty tucker, three blocks down was trapped and says a neighbor helped pull her out from under her crumbled walls. >> the most horrible noise i've heard in my life. >> reporter: she walked to find wounded neighbors stu through the streets. doctors set up a makeshift triage in a nearby field. >> did you know anyone who was killed in this? >> yes, i do. this is a small, private community. >> reporter: tonight investigators are trying to determine what started the fire at the plant with its huge tanks of highly flammable anhydrous ammonia, used to treat fertilizer. >> we're way too early in the investigation to speculate on causes or what may have occurred. >> reporter: but the timing of the disaster is haunting.

20 years ago this week, the compound of the branch davidian cult in nearby waco, came to a fiery end after a showdown with federal agents. in west tonight, 160 people are recovering from their injuries. the mayor says up to 45 people are still missing as people search the rubble for survivors. late today authorities released the name of the first casualty in this explosion. captain kenny harris, who actually worked for the dallas fire department, but lived in west, responded to the call. tonight they're hailing him as a hero. diane? >> again, steve, thank you. and as you said, they've said it's still too early to come up with any cause or any motive in what happened. what we do know is that the little texas town is a kind of texas version of a norman rockwell painting. just a few thousand people, as you heard. and cecilia vega spent the day with people who told her every rescuer, every person rescued, was someone you know. >> reporter: shattered and broken.

>> oh, my god. >> a war zone. every window is out. and the house, the whole ceiling, it looks like it come off the foundation and set back down. the bricks are all off the houses. >> reporter: mike maler barely made it out alive. his family's brick house, it's completely gone. just like so many of his neighbors. >> i have relatives just down the road and you can't get in touch with them. if you do, the cellphone is out. and i want to get in touch with them, so that's why i'm here. just to see if they're even alive. >> reporter: in a place where everyone knows everyone else, the injured and missing are all someone's family, someone's friend, a familiar face. west, texas, is the heartland of america, home to just 2,800 people -- and the annual barbecue cook-off by volunteer firefighters. many of those same firefighters running into yesterday's blaze, as others ran out. so many still unaccounted for. their station flags today -- at half staff. >> how many people do you think

you know who were hurt in that? >> i probably know all of them. >> reporter: today the streets of west, texas, are battered and bruised. so are its residents. >> this is from the blast? >> yes. >> reporter: the blast so strong, it knocked down eldin pavelka right out of his chair -- his windows blown out. his metal garage door, twisted. but he calls himself one of the lucky ones. >> what e you feeling toy?ankf still here.e lre >> reporter: mr. pavelka lives right up the road, not too far . but this is the scene in much of west, texas, buildings, homes, that are boarded up, homes with major damage like this one. some of them demolished. the blast site, half a mile away from here. just shows you how strong that blast was. >> it was that powerful and a whole nation is standing with everyone there tonight. thank you, cecilia. and a note about the wild weather pummelling the nation's mid section today. look at the map.

a mad mix of snow, tornadoes, and floods. in chicago, a storm dumping five inches of rain on the city in 12 hours. that and a water main break on the city's southeast side causing a huge sink hole to open up. one man hospitalized after trying to drive around the hole that quickly grew to 40 feet. that driver said to be in good condition tonight. and still ahead on "world news," the elvis impersonator. ♪ >> now the suspect in the poison ricin scare. suspected of mailing poison to the president. who is this man? that's next. most people think that after an accident, you'll have to pay five hundred bucks for your deductible. the truth? at allstate, you could pay zero. allstate gives you a hundred dollars

off your deductible the day you sign up. then another hundred off every year you don't have an accident. let the good handsuctible the day you sign up. reward your safe driving with a deductible that goes away. ♪ ductible rew one more way you're in good hands with allstate. ♪ can you start the day the way you want? can orencia (abatacept) help? [ woman ] i wanted to get up when i was ready, not my joints.

[ female announcer ] could your "i want" become "i can"? talk to your rheumatologist. orencia reduces many ra symptoms like pain, morning stiffness and the progression of joint damage. it's helped new ra patients and those not helped enough by other treatments. do not take orencia with another biologic medicine for ra due to an increased risk of serious infection. serious side effects can occur including fatal infections. cases of lymphoma and lung cancer have been reported. tell your doctor if you are prone to or have any infection like an open sore or the flu or a history of copd, a chronic lung disease. orencia may worsen your copd. [ woman ] here's information you need to know. orencia is available in two forms, infusion and also self-injection. talk to your doctor to see if encia is rht for you. and see if y can change "i want" to "oh, yes i can!" and his new boss told him two things -- cook what you love, and save your money. joe doesn't know it yet, but he'll work his way up from busser to waiter to chef beng a restaurant

specializing in fish and game from the great northwest. he'll start investing early, he'll find some good people to help guide him, and he'll set money aside from his first day of work to his last, which isn't rocket science. it's just common sense. from td ameritrade. and in the news today as well, the man accused of sending those letters laced with poison to the president and a senator, was in court today. and tonight, strange new details emerging. he's said to be an elvis impersonator, obsessed with conspiracy theories and with a personal link to one of his targets. abc's matt gutman has the portrait of this man coming into focus tonight. ♪ >> reporter: this is paul kevin curtis, the man in custody for allegedly terrorizing the federal government for two days. ♪

a flamboyant celebrity impersonator with his own youtube channel and an unusual ring letters to the government from this sleepy mississippi town. and accordg investigators, on april 8th, three of his letters were laced with the toxic chemical ricin. "there are still missing pieces. maybe i have your attention now, even if that means someone has to die." the form letters were sent to president obama, senator roger wicker of mississippi, and mississippi judge sadie holland, who opened hers. >> a white kind of like grainy-type substance loose in the envelope. >> reporter: prosecutors say the missing pieces in the letters could refer to curtis' obsession with the sale of black market body parts. he's even written a book and tweeted about it. >> reporter: in a statement, his brother said, "we have no reason to believe kevin would be involved. we love him, and look forward to getting answers to make sense of all this." we met his neighbor lacey ross

today. what do you think about the fact that he might have been cooking up ricin right next door? >> terrifying. really scary. i have two daughters. just knowing it could be that close to my children. >> reporter: just moments ago, members of the hazmat team arrived. a breached the door. took down the security camera. a lot of men are heavily armed, starting to gather evidence. the big question, what are they going to find inside? >> on the scene, thank you, matt gutman. and coming up next here -- ♪ >> do you know how old superman is and how he looked when it all began? that's next. [ all ] fort benning, georgia, in 1999. s often handed down from generation to generation because it offers a superior level of protection

is without equal. begin your legacy. get an auto-insurance quote. usaa. t it means to serve. trust your instincts to make the call. to treat my low testosterone, my doctor and i went with axiron, the only underarm low t treatment. axiron can restore t levels to normal in about 2 weeks in most men. axiron is not for use in women or anyone younger than 18 or men with prostate or breast cancer. women, especially those who are or who may become pregnant and children should avoid contact where axiron is applied as unexpected signs of puberty in children or changes in body hair or increased acne in women may occur. report these symptoms to your doctor. tell your doctor about all medical conditions and medications. serious side effects could include increased risk of prostate cancer; worsening prostate symptoms; decreased sperm count; ankle, feet or body swelling; enlarged or painful breasts; problems breathing while sleeping; and blood clots in the legs.

e fects include skin redness or irritation where applied, increased red blood cell count, headache, diarrhea, vomiting, and increase in psa. ask your doctor about the only underarm low t treatment, axiron. but with advair, i'm breathing better. so now i can help make this a great block party. ♪ [ male announcer ] advair is clinically proven to help significantly improve lung function. unlike most copd medications, advair contains both an anti-inflammatory and a long-acting bronchodilator working together to help improve your lung function all day. advair won't replace fast-acting inhalers for sudden symptoms and should not be used more than twice a day. plpeoe with copd taking advair may have a higher chance of pneumonia. advair may increase your risk of osteoporosis and some eye problems. tell your doctor if you have a heart condition or high blood pressure before taking advair. ask your doctor if including advair could help improve your lung function.

[ male announcer ] advair diskus fluticasone propionate and salmeterol inhalation powder. get your first prescription free and save on refills at advaircopd.com. and we begin our instant index tonight with a birthday for superman, who is 75 years old today. here is the first ten-cent comic book cover and that was 75 years ago. it's now worth more than $2 million. over the decades, of course, we've watched him muscle up and go to tv with george reeves. and then on to movies with chris reeve. the kryptonite of time has not slowed him down. a new superman movie is due out in june. and some other true-life supermen, even older. retired lieutenant colonel, richard cole is 97 and still he

landed a b-52 bomber this week. it was the reunion of world war ii veterans in florida. there are only four left who had the sheer nerve to fly that april 18th raid on japan i 1942, afteor it was the raid made famous in the movie "30 seconds over tokyo." they say it will be their last reunion, and they're opening a bottle of cogniac from 1896. the year commander doo little was rn w, lieutenant colonel cole, i realize i just said "b-52," i know you were flying a b-25. and a toast to all of you from all of us here tonight. >> and if you see something out there crackling for our instant index, tweet it to me @diane sawyer. it brings us to a question. are the bravest among us the true heroes, born or made? we have an answer in a moment. wer in a moment. [ male announcer ] when you're going the distance,

it's nice to have the experience and commitment to go along with you. aarp medicare supplement insurance plans, insured by unitedhealthcare insurance company. keep dreaming. keep doing. go long. insured by unitedhealthcare insurance company. and you wouldn't have it any other way.e. but your erectile dysfunction - you know, that could be a question of blood flow. cialis tadalafil for daily use helps you be ready anytime the moment's right. you can be more confident in your ability to be ready. and the same cialis is the only daily ed tablet approved to treat ed and symptoms of bph, like needing to go frequently or urgently.

tell yr doctor about all your medical conditions and medications, and ask if youis heanoh your medical conditions anfor sexual activity. do not take cialis if you take nitrates for chest pain, this may cause an unsafe drop in blood pressure. do not drink alcohol in excess with cialis. side effects may include headache, upset stomach, delayed backache or muscle ache. to avoid long-term injury, seek immediate medical help for an erection lasting more than four hours. if you have any sudden decrease or loss in hearing or vision, or if you have any allergic reactions such as rash, hives, swelling of the lips, tongue or throat, or difficulty breathing or swallowing, stop taking cialis and get medical help right away. ask your doctor about cialis for daily use and a 30-tablet free trial. are proven to be effective pain relievers. tylenol works by blocking pain signals to your brain. bayer advanced aspirin blocks pain at the site. try the power of bayer advanced aspirin.

and finally from us tonight, someone said that courage is just fear that has said its prayers. but we wondered if courage is also a place in the mind, or in the heart. so abc's dan harris went looking for the answers, all around us this week in texas and boston, as the nation was shaken and re-inspired. >> reporter: in boston this week, america bore witness to a college student who, after running 26 miles, gave the shirt off his back to treat a victim's wound. the grieving father who'd come to hand out flags in honor of his dead sons who leapt into the fray. and the off-duty firefighter who gave aid to a badly-injured boy. why did you do it? >> you just do it. you're really glad that you're

there and you can do your part to make a difference. >> reporter: in west, texas, overnight, similar tales of heroism. william birch pulled the injured out of a demolished nursing home. >> you have to reach out and help those who can't help themselves. >> reporter: what causes someo to run toward danger when others are running away? scientists say having a tctim,e the boyfriends who shielded their girlfriends in the aurora movie theater massacre, or to a place, as in boston and in texas, can make difference. but ultimately, said there harvard ofessor, it's a rare quality that is nearly impossible to predict. >> none of us know whether he have a hero inside? >> until we're faced with a crisis situation that puts extraordinary demand on ordinary people. >> reporter: traditionally mankind has been viewed as essentially selfish, survival of the fittest and all that, but the willingness to risk our own lives to help strangers may be

what has allowed us to survive as a species and certainly to endure disasters like we've seen this week. dan harris, abc news, boston. >> and we hope you will tune in tonight for "nightline." i'll see you right back here again tomorrow. goodnight. from texas tonight scenes of utter devastation. you're going to hear from a bay area expert who tells abc 7 news industry values profits over safety. >> abc 7 news captures a return to ground zero. you'll see the video that has

the fbi focused on finding two men. >> a suspect in the murder of an off duty paramedic, take a looking into the surveillance video that put police on his trail. >> and from the peninsula, nasa shows off technology that will pay big dividends over the summer fire season. >> these two men are now the focus of a nationwide manhunt. >> and this is what is left of the fertilizer plant that blew up in texas last night and took half a town with it. good evening, everyone, i'm carolyn johnson. >> we have major vemments on both stories tonight but we're going to begin in texas where the death toll is rising. now, it could be as high as 40 peoplement today we began getting pictures like these, homes in runz for blocks around the plant that blew up last night, destroyed by

at -- by the force of the blast. we sent laura anthony to the scene in the town of west about an hour and a half from dallas. and laura is there tonight with this report.>> i guess ammt catchingir i heard go now, you're about to die. >> ryan and his young family lived ine parmd billings blown to by wednesday night's explosion. he knew when the plant was just on fire waits time to take his young son and wife out of the house. >> 20 seconds we got in the car and started to leave. and then, i turned to the right and about 10 seconds later that thing exploded. it pushed the car down. the car went up on the side on two wheels. >> just a big crack of thunder. >> but this friend was still home when the